Both lower wishbones and steering rod linkages parallel to the ground with the upper wishbones inclined slightly upwards are good starting positions to minimise bump steer.
My car got pinged at inspection for too much bump steer, however on my 1982 chassis the steering rack is mounted in two aluminium clamping blocks, attached to a chassis member across the front of the engine bay, these two blocks where machined in such a way that the rack tube could be in a low or high position, depending on which orientation of the blocks was used, so a few minutes with some spanners and a change of rack mounting height got the tick, just had to do a steering alignment to get it all pointing in the right direction. transformed the road manners, so much nicer to drive now, no more continuous steering correction. Bump steer is not your friend.
Basically to simplify without doing lots of research..
The idea of alleviating bump steer is to make the top wishbone, bottom wishbone and steering arm all follow the same arc upward and inwards as you hit a bump with one wheel.
Otherwise as the fixed top and bottom wishbone move up, they force the steering arm across giving kickback on the steering wheel.
If you can make all 3 closely follow the same trajectory by altering the position (height) of the steering rack, you hit the bump and nothing happens to the steering.
you will never make them all move in the same arcs since their lengths and datum pivots points vary, you are however trying to gain co operationn between these three links, therefore any bump steer you have works in your favour and doesn't encourage you to exit stage left on a bumpy B road
I hope that's the angle Jonathan.
Steering tie roads look to slope upwards towards wheels. Sure raising the rack will make a big difference.
Thank you Ian, I have a lot of reading to do, but is the aim to get the tie rods perfectly horizontal please?
I think parallel to wishbones, but not sure of the exact science. I am lucky enough to have Boss racing a few miles from home
Both lower wishbones and steering rod linkages parallel to the ground with the upper wishbones inclined slightly upwards are good starting positions to minimise bump steer.
James
My car got pinged at inspection for too much bump steer, however on my 1982 chassis the steering rack is mounted in two aluminium clamping blocks, attached to a chassis member across the front of the engine bay, these two blocks where machined in such a way that the rack tube could be in a low or high position, depending on which orientation of the blocks was used, so a few minutes with some spanners and a change of rack mounting height got the tick, just had to do a steering alignment to get it all pointing in the right direction. transformed the road manners, so much nicer to drive now, no more continuous steering correction. Bump steer is not your friend.
Did you recheck the bump steer after doing the alignment adjustments as this will impact on it......
Basically to simplify without doing lots of research..
The idea of alleviating bump steer is to make the top wishbone, bottom wishbone and steering arm all follow the same arc upward and inwards as you hit a bump with one wheel.
Otherwise as the fixed top and bottom wishbone move up, they force the steering arm across giving kickback on the steering wheel.
If you can make all 3 closely follow the same trajectory by altering the position (height) of the steering rack, you hit the bump and nothing happens to the steering.
That's the theory..
22daz
you will never make them all move in the same arcs since their lengths and datum pivots points vary, you are however trying to gain co operationn between these three links, therefore any bump steer you have works in your favour and doesn't encourage you to exit stage left on a bumpy B road